116
R.Z. Uslu Kobak et al. / Dyes and Pigments 86 (2010) 115e122
n-pentanol. Furthermore, the voltammetric and spectroelec-
trochemical properties of the hexyloxy tetrapyrazinoporphyrazines
were demonstrated.
procedure of the pyrazine dicarbonitriles except that DMF was used
instead of ethanol in the precipitation process. The yield of pale
yellow solid was 0.18 g (52.5%). IR, ymax (cmꢁ1): 3036 (CH,
aromatic), 2923 (CH, aliphatic), 2238 (C^N), 1445, 1345, 1146,
1064e1030 (CeO), 748, 692. MS(m/z): 341,874 [Mþ]. 1H NMR
2. Experimental
(CDCl3, d), ppm: 7.45e7.36 (m, 10H, AreH), 5.56 (s, 4H, OeCH2).
2.1. Equipment and materials
Calculated for C20H14N4O2: C 70.17; H 4.12; N 16.37%. Found: C
69.97; H 3.94; N 16.08%.
Electronic spectra were recorded on a Scinco SD-1000 double-
beam UVeVis spectrophotometer and IR spectra on a Perkin Elmer
Spectrum One FT-IR (ATR sampling accessory) spectrophotometer.
Elemental analyses were performed in the Instrumental Analysis
Laboratory of the TUBITAK Marmara Research Centre using Carlo
Erba 1106. 1H NMR spectra were recorded in CDCl3 solution using
a Bruker 250 MHz NMR spectrometer. Mass spectra were measured
on a Bruker Daltonics MicroTOF mass spectrometer. All starting
materials were purchased from major suppliers and used without
any further purification. Dimethylformamide was dried over 4 Å
molecular sieves and 5,6-dichloropyrazine-2,3-dicarbonitrile (1)
was obtained in a two step synthesis from diaminomaleodinitrile
(DAMN) according to procedures described in the literature [4].
2.2.2. General procedure of octakis(hexyloxy)
pyrazinoporphyrazinato metal (II) (6e8)
In order to synthesize the metal pyrazinoporphyrazine,
a synthesized pyrazine dinitrile (0.3 mmol of 2, 3, 4 or 5) was reacted
with the convenient anhydrous metal salt (zinc (II) acetate, cobalt
(II) chloride or copper (II) chloride (0.15 mmol)) in the presence of
10 m
L DBU and 1.2 mL of n-hexanol at 135 ꢀC for 6 h under nitrogen
atmosphere. After cooling, crude product was precipitated by
addition of MeOH (3 mL). The precipitate was filtered off, washed
with MeOH and acetone. The product was purified by column
chromatography on silica gel (SiO2) using different solvent or
solvent mixture as eluent.
2.2. Synthesis
2.2.2.1. Octakis (hexyloxy)pyrazinoporphyrazinato zinc (II) (6). This
compound was synthesized according to the general procedure of
octakis- (hexyloxy)pyrazinoporphyrazinato metal (II). The amounts
of the reagents used were as follows: 0.1 g of a dinitrile derivative 2
(0.25 mmol), 3 (0.3 mmol), 4 (0.22 mmol) or 5 (0.3 mmol) and
anhydrous zinc (II) acetate [(0.023 g, 0.125 mmol), (0.027 g,
0.15 mmol), (0.02 g, 0.11 mmol) or (0.027 g, 0.15 mmol) for 2, 3, 4, 5;
respectively]. The crude title compound isolated from the mixture
was then purified on silica gel column using methanol/chloroform
1:100 mobile phase. When 2, 3, 4 or 5 was used as the precursor,
yield was 0.024 g (27.5%); 0.028 g (26.9%); 0.014 g (18.4%); 0.022 g
(21.2%), respectively. IR, ymax (cmꢁ1): 2956e2858 (CH, aliphatic),
2.2.1. General procedure of pyrazine dicarbonitriles (2e5)
5,6-dichloropyrazine-2,3-dicarbonitrile 1 (0.2 g, 1 mmol) and
the corresponding hydroxyl derivative that is p-nitrophenol for 2
(0.28 g, 2 mmol), p-cresol for 3 (0.2 mL, 2 mmol), 3-(diethylamino)
phenol for 4 (0.33 g, 2 mmol), benzyl alcohol for 5 (0.2 mL, 2 mmol)
was stirred in 35 mL THF at 65 ꢀC. Reaction in the presence of
triethylamine (0.3 mL, 2.2 mmol) as a base required approximately
18 h to achieve the desired pyrazine dicarbonitriles. The reaction
mixture was filtered and the filtrate evaporated to dryness. The
residue was dissolved in ethanol and then precipitated by addition
of water; the yellow precipitate was collected by filtration and
washed with cold hexane and diethyl ether. The residue was further
recrystallized from acetone/hexane.
1638,1441,1120,1062 (CeO), 983,739. 1H NMR (CDCl3)
(m, 16H, OeCH2), 2.33e1.23 (br, 64H, CH2), 1.01 (br, 24H, CH3).
UVeVis lmax(nm) (log ) in CHCl3: 361 (5.34), 624 (5.11). Calculated
d: 4.44e4.20
3
for C72H104N16O8Zn:C 62.34; H 7.56; N 16.16%. Found: C 62.04; H
7.78; N 15.96%.
2.2.1.1. 5,6-Bis(4-nitrophenoxy)pyrazine-2,3-dicarbonitrile (2). The
yield of yellow solid was 0.32 g (78.8%). Melting point (m.p):
250e255 ꢀC. IR, ymax (cmꢁ1): 3114e3074 (CH, aromatic), 2240
(C^N), 1519, 1346, 1231 (AreOeAr), 1154, 851, 748. 1H NMR (d6-
2.2.2.2. Octakis(hexyloxy)pyrazinoporphyrazinato cobalt (II) (7). This
compound was synthesized according to the general procedure
employed for octakis (hexyloxy)pyrazinoporphyrazinato metal (II).
The amounts of the reagents were employed: 0.1 g of a dinitrile
derivative 2 (0.25 mmol) or 3 (0.3 mmol), anhydrous cobalt (II)
chloride [(0.016 g, 0.125 mmol) or (0.019 g, 0.15 mmol) for 2 and 3;
respectively]. The crude title compound isolated from the mixture
was then purified on silica gel column using first THF/chloroform
1:5 as the mobile phase and then once more with 2/100 methanol/
chloroform. When 2 or 3 was used as the ligand, the yield was
0.033 g (38.4%) and 0.037 g (36%), respectively. IR, ymax (cmꢁ1):
2956e2858 (CH, aliphatic), 1640, 1450, 1137, 1073 (CeO), 981,750.
acetone,
d), ppm: 8.50e7.67 (m, 8H, AreH). Calculated for
C18H8N6O6: C 53.47; H 1.99; N 20.79%. Found: C 53.51; H 2.05; N
20.84%.
2.2.1.2. 5,6-Bis(4-methylphenoxy)pyrazine-2,3-dicarbonitrile (3). The
yield of pale yellow solid was 0.27 g (79%). M.p: 235e242 ꢀC. IR,
ymax (cmꢁ1): 3036 (CH, aromatic), 2960e2925 (CH, aliphatic) 2238
(C^N), 1443, 1262e1238 (AreOeAr), 1154, 1017, 808. 1H NMR (d6-
acetone, d), ppm : 7.36e7.21 (m, 8H, AreH), 2.38 (s, 6H, CH3). MS(m/
z): 341,038 [Mþ]. Calculated for C20H14N4O2: C 70.17; H 4.12; N
16.37%. Found: C 70.35; H 4.26; N 16.16%.
MS: (m/z): 1380.9 [Mþ]. UVeVis lmax(nm) (log
3) in CHCl3: 334
(5.26), 608 (5.09). Calculated for C72H104N16O8Co: C 62.64; H 7.59; N
16.23%. Found: C 62.98; H 7.87; N 16.55%.
2.2.1.3. 5,6-Bis[3-(diethylamino)phenoxy]pyrazine-2,3-dicarbonitrile
(4). The yield of pale yellow solid was 0.31 g (67%). M. p:
137e139 ꢀC. IR, ymax (cmꢁ1): 3078 (CH, aromatic), 2974e2934 (CH,
aliphatic) 2236 (C^N), 1613, 1446, 1270e1232 (AreOeAr), 1129,
2.2.2.3. Octakis(hexyloxy)pyrazinoporphyrazinato copper (II) (8). This
compound was synthesized according to the general procedure
used for octakis (hexyloxy)pyrazinoporphyrazinato metal (II). The
amounts of the reagents were used as follows: 0.1 g of a dinitrile
derivative 2 (0.25 mmol) or 3 (0.3 mmol), anhydrous copper (II)
chloride [(0.017 g, 0.125 mmol) or (0.02 g, 0.15 mmol) for 2 and 3;
respectively]. The title compound isolated from the mixture was
then purified on silica gel column using methanol/chloroform
2:100 as the mobile phase. When 2 or 3 was used as ligand, yield
1021, 760. 1H NMR (d6-acetone,
d), ppm: 7.30e6.48 (m, 8H, AreH),
3.45e3.36 (q, 8H, NeCH2), 1.18e1.08 (t, 12H, CH3). Calculated for
C26H28N6O2: C 68.40; H 6.18; N 18.41%. Found: C 68.12; H 6.46; N
18.16%.
2.2.1.4. 5,6-Bis(benzyloxy)pyrazine-2,3-dicarbonitrile (5). Synthesis
and purification were carried out as outlined for the general